Treatment of hydrocarbon distillates



i atented Nov. 4, 1.95?

TREATMENT. OF HYDROCARBON DISTILLATES Robert H. Rosenwald, Western Springs, Ill;, as

si ner to Universal Oil Products Company, Chicago, IlL, a corporation of Delaware,

No Drawing. Application March 1,1951, Serial No. 213,468

13 Claims.

This invention'relates to thetreatment'of hydro'carbon distillates and more particularly to a.

novel method of accelerating sweetening of sour hydrocarbon distillates.

One method of sweetening a sour hydrocarbon distillate and particularly cracked gasoline en-..

tails the use of a phenylene diaminecompound. Because the phenylene diamine compound-also serves as an oxidation inhibitor, this process is referred toas inhibitor sweetening. However,

it has been found that in some cases inhibitor sweetening will not occur and in other cases the sweetening will not occur within a sufiiciently short time to be a practical refinery operation. For example, in some cases the gasoline does not become sweet in storage for several days or more. Due to shortage of storage capacity or in order to comply with shipping schedules or for other reasons, it is'of'ten necessary to transport or use the gasoline promptly, and the refiner cannot afford to wait until sufficient time has elapsed for the gasoline to become sweet. The present invention is directed to a novel method of accelerating the inhibitor sweeteningrcaction.

In one embodiment the present invention relates to the process of sweeteninga sour hydrocarbon distillatewhich comprises contacting said distillate in the'presence of air with a phenylene diamine compound, an alkaline material and a solvent for said alkaline material, said solvent havinglimited solubility in said distillate.

In a specific embodiment the present invention relates to the process of sweetening sour cracked gasoline which comprises contacting said gasoline with N,N'-di-secondary-butyl-p-phenylene diamine in the presence of air and an alcoholic solution of caustic.

As hereinbefore set forth, the inhibitor sweetening reaction does not occur with all sour hydrocarbon distillates and in other cases the rate of sweetening is so slow as to be impractical from a commercial viewpoint. I have discovered that the inhibitor sweetening reaction is accelerated when effected in the presence of a particular type of solution of an alkaline material. I It is an essential feature of the present invention that the solvent employed for the alkaline material possesses certain particular properties. first place, the solvent must be one in which the alkaline material is substantially soluble and, in the second place, the solvent must be one which is of only limited solubility in the hydrocarbon distillate; In the third place, the solvent must possess a selective solubility for mercaptans.

In order'for the alkaline material to accelerate In the th inhibitor sweetening reaction it is essential that the alkaline material be intimately dispersed within the hydrocarbon distillate so that it will be in intimate .contact with the mercaptans and/ or phenylene diamine compound and thereby will enhance, facilitateor catalyze the desired sweet-.- ening reaction.

When utilizing a solvent which is readily misciblel in the. hydrocarbon distillate, the solvent will tend to enter. into the hydrocarbon phase and thereby will result in precipitating or 3 settling out. of the alkalinematerial. In this way, the

alkaline material is not made available to cat-.

alyze or direct the inhibitor sweetening reaction. For this reason and as will be shown in thefollowing examples, an aqueous solution of caustic cases it may be necessary to introduce air from.

an extraneous source, particularly when the distillate is storedin tanks having floating roofs which'serve to exclud air. It is understood that oxygen or other oxygen-containing gases may be used in place of air.

Any suitable phenylene diamine compound may beemployed in accordance with the present invention. A preferred phenylene diamine. compound comprises N,N-di-secon dary-butyl-pphenylene diamine. Other suitable phenylene diamine compounds include N,N'-di-isopropyl-p phenylene diamine, N,N-di-secondary-amyl-p-.

phenylene diamine, N-isopropyl-N'-secondary butyl-p phenylene diamine, N-isopropyl-Nf-sec-.

ondary-amyl-p-phenylene diamine, N-secondary butyl N secondary amyl p phenylene diamine, etc. It is understood that other substituted phenylene diamines in which. one or more alkyl radicals are substituted for the amino hydrogens or are attached to the phenyl. rings, these alkyl radicals being the same or different, are comprised within the scope of the present invention but are not necessarily equivalent. The phenylene diamine compound is generally uti-'- lized in a concentration of from about 0.0001% 1 to about 1.0% by weight of the hydrocarbon distillate and preferably of from about 0.001% to about 0.1% by weight.

Any suitable alkaline material may b used in accordance with the present invention. The alkaline material should be hydrocarbon insoluble in order that the alkaline material subsequently may be separated readily from the hydrocarbon distillate. Sodium hydroxide is particularly preferred because of its high effectiveness, ready solubility and low cost. Other suitable but not necessarily equivalent alkaline materials include (1) compounds and particularly the hydroxides of the alkali metals including potassium, lithium, ruthenium and caesium, (2) compounds and particularly the hydroxides of the alkaline earth metals including calcium, strontium and barium, and (3) organic basic compounds which are substantially insoluble in hydrocarbons including (a) polyamines, such as diethylene triamine, triethylene tetramine, tetraethylene pentamine, 1,2-diaminopropane, 13- diaminobutane, 1,3,5-triaminopentane, 1,3,6-triaminohexane, l,3,5,7-tetraminoheptane, etc., (b) aminoalcohols including aminoethanol, diaminopropanol, triaminobutanol, tetraminopentanol, etc. and (c) quaternary ammonium compounds including tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, tetramethyl ammonium methoxide, tetramethyl ammonium ethoxide, tetraethyl ammonium ethoxide, etc.

The alkaline material will be used in an amount suflicient to effect the improved results, which amount may vary depending upon the particular alkaline material to be employed. It is believed that the alkaline material functions as a catalyst and thus will be effective in low concentrations. The amount of alkalinity provided by the alkaline material, the alkalinity being determined by conventional titration methods, should be at least about one pound per 1000 barrels of hydrocarbon distillate. Stated otherwise,

the concentration of alkaline material should be at least about 0.0025% by weight of the hydrocarbon distillate and generally will be within the range of from about 0.003% to 1% or more. Higher concentrations of the alkaline material are not objectionable, although no increased benefits may result from the use of excessively large amounts of the alkaline material.

Any suitable solvent in which the alkaline material is substantially soluble and which is of only limited solubility in hydrocarbons may be used in accordance with the present invention. Particularly preferred solvents comprise alcohols, including methyl alcohol, ethyl alcohol, propyl alcohol, etc. Other suitable but not necessarily equivalent solvents include the glycols such as, ethylene glycol, diethylene glycol, propylene glycol, pinacol, glycerol, erythritol, Cellosolve, methyl Cellosolve, butyl Cellosolve, etc. Potassium isobutyrate and similar compounds serve the function of increasing contact of caustic with the mercaptans contained in hydrocarbon distillates and, therefore, may be used within the scope of the present invention. When the alkaline material is an inorganic compound, the solvent may comprisethe organic basic compounds as hereinbefore set forth because these compounds will function as a solvent for the more insoluble inorganic basic material. Thus, when caustic is utilized as the alkaline material, the solvent may comprise an organic material such as ethylene diamine, ethylene triamine, triethylene tetramine, 1,2-diaminopropane, 1,3-diaminobutane, hexamethylene tetramine, etc., or amino alcohols such as 5-amino 4 octanol, l-amino 2 hexanol, 2-amino-1-heptanol, etc. The use of the amines and amino alcohols will serve the dual function of acting both as a solvent for the inorganic alkaline material and also to contribute to the desired alkalinity for accelerating the sweetening reaction. The amount of solvent to be employed will vary with the particular alkaline material and the particular solvent. Solutions ranging from about 5% to about 75% by weight of the alkaline material in the solvent may be employed although it generally is preferred to use solutions containing from about 10% to about 50% by weight of the alkaline material.

As most of the solvents hereinbefore set forth are miscible with water, it is also within the scope of the present invention to include water in the solution of alkaline material. This has the advantage of reducing the amount of solvent required and also of assisting in subsequent separation of the alkaline material from'the hydrocarbon distillate. However, the amount of water to be used in the solution must not be too large to interfere with intimate contact of the alkaline material with the mercaptans in the hydrocarbon distillate. As a general rule, the amount of water to be employed should not exceed the amount of nonaqueous solvent employed and preferably is within the range of from about 25% to about 75% by volume of the nonaqueous solvent.

The process of the present invention may be effected in any suitable manner whereby the hydrocarbon distillate is intimately contacted with the phenylene diamine compound and a solution of the alkaline material. In a preferred method the phenylene diamine compound and the solution of alkaline material, either in commingled state or as separate streams, are commingled with the hydrocarbon distillate, and the resultant mixture is passed through suitable mixing devices, such as duriron mixers, orifice mixers, etc. The intimately mixed dispersion is then introduced into a storage tank which may contain suitable stirring means, such as mixing paddles, etc. in order to effect further mixing of the components therein. After the desired time, which in accordance with the present invention will be comparatively short, mixing in the tank is discontinued and the alkaline material allowed to settle to the bottom of the tank as a separate phase. When sufiicient air is not contained in the hydrocarbon distillate, air may be introduced directly to the storage tank or it may be introduced to the stream of hydrocarbon distillate before the mixing devices and either together with or separately from the phenylene diamine compound and/or solution of alkaline material. While the method hereinbefore set forth is preferred, it is understood that any other suitable method for effecting intimate contact between these components may be utilized in accordance with the present invention.

The inhibitor sweetening reaction is readily effected at atmospheric temperature, which generally ranges from about 50 to about F. However, in some cases it may be desirable to employ higher temperatures which may range to or more.

While this process is particularly applicable for the treatment of cracked gasoline, it is understood that With suitable modifications the process may be utilized for the treatment of straight run or natural gasolines, higher boiling hydrocarbon distillates including kerosene, gas oil, diesel fuel, etc.

The following examples are introduced to illustrate further the novelty and'utility of the present invention but not with the intention of unduly limiting the same.

EXAMPLE I A series of tests was made to directly compare the results obtained when utilizing (1) a methanol solution of sodium hydroxide, said solution consisting of one part by weight of sodium'hydroxide, two parts by weight of methyl alcohol and one part by weight of water, with (2) an aqueous solution of sodium hydroxide. The hydrocarbon distillate in this series of tests comprised cyclohexene to which had been added approximately 1.5% by weight of mercaptan sulfur as n-butyl mercaptan. The phenylene diamine compound used in these tests was N,N'-di-secondary-butyl-p-phenylene diamine and this compound was used in an amount of about 0.4% by Weight.

These tests were continued for 24 hours and it was found that definite advantages resulted from the use of the methanol solution of caustic as comparedto the aqueous solution. These results are shown in the following table:

Table Methanol Aqueous solution solution of caustic of caustic Rate of Oxidation, Mols O2/mol RSH/hour. 0.2 0. 08 Total absorption of oxygen, Mols O2/mo1 RSH 0.37 0. 42

Oxygen absorbed as peroxide, percent 0 4 EXAMPLE II A thermally cracked gasoline having a mercaptan sulfur content of 0.008% by weight may be treated with 0.01% by weight of N,N'-disecondary-butyl-p-phenylene diamine and 1% by weight of a solution of caustic in a solvent comprising 60% by volume of denatured alcohol and 40% by volume of water, at a temperature of 80 F.

The gasoline, when treated in the above manner, will become sweet in less than 24 hours in storage. As hereinbefore set forth, this prompt sweetening of the gasoline represents a major advantage to the refiner in permitting him to transport and use the gasoline within a short time after production thereof.

EXANIPLE III Gasoline similar to that described in Example II may be sweetened by contacting with 0.005% by weight of N,N'-di-isopropyl-p-phenylene diamine and 3% by weight of a solution of 20% by weight of potassium hydroxide in ethyl alcohol.

EXAMPLE IV Cracked gasoline similar to that described in Example II may be sweetened by treatment with 0.02% by weight of N, N'-di-secondary-amyl-pphenylene diamine and 2% by weight of a solution consisting of 50% by volume of tetramethyl ammonium hydroxide in a solvent comprising 60% by volume of ethylene glycol and 40% by volume of water.

EXAMPLE V .A cracked light gas oil having a mercaptan sulfur content of about 0.003% by weightmay be sweetened by treatment with 0.005% byweight' of N,N'-di-secondary-butyl-p-phenylene diamine and 1% by weight of asolution of caustic in a solvent comprising 20% potassium isobutyrate and methyl alcohol. The phenylene diamine compound and alkaline solution, alone or with added air, are commingled with the gas oil and the resultant mixture is passed through a duriron mixer and then is supplied to a storage tank containing a mixing paddle and steam coils to heat and maintain the mixture at a temperature of F. After 12 hours the heating and mixing are discontinued and the alkaline compound is allowed to settle to the bottom of the storage tank as a separate phase.

I claim as my invention:

1. The process of sweetening a sour hydrocarbon distillate which comprises contacting said distillate in the presence of air with a phenylene diamine, an inorganic alkaline material and a. solvent for said alkaline material, said solvent having limited solubility in said distillate and selected from the group consisting of amines and amino alcohols.

2. The process of sweetening a sour hydrocarbon distillate which comprises contacting said distillate in the presence of air with a phenylene diamine, caustic and a solvent therefor, said solvent having limited solubility in said distillate and selected from the group consisting of amines and. amino alcohols.

3. The process of sweetening a sour hydrocarbon distillate which comprises contacting said distillate in the presence of air with a phenylene diamine and a solution of an alkali metal hydroxide in a solvent selected from the group consisting of amines and amino alcohols.

4. The process of sweetening a sour hydrocarbon distillate which comprises contacting said distillate in the presence of air with N.N-di-secondary-butyl-p-phenylene diamine and a solution of caustic in a solvent selected from the group consisting of amines and amino alcohols.

5. A method of sweetening a sour cracked hydrocarbon distillate which comprises contacting said distillate in the presence of air with a phenylene diamine, an inorganic alkaline material and a solvent therefor, said solvent having limited solubility in said distillate and selected from the group consisting of amines and amino alcohols.

6. The process of claim 5 further characterized in that said alkaline material comprises an alkali metal hydroxide.

'7. The process of claim 5 further characterized in that said alkaline material comprises caustic.

8. The process of claim 5 further characterized in that said alkaline material comprises an alkaline earth metal hydroxide.

9. The process of claim 5 further characterized in that said solvent comprises a polyamine.

10. The process of claim 5 further characterized in that said solvent comprises diethylene triamine.

6 13. A method of sweetening sour cracked gasoline which comprises contacting said gasoline with from about 0,001% to about 1% by weight of N,N'-di-secondary-butyl p phenylene diamine in the presence of air and at least 0.0025% by weight of an inorganic alkaline material dissolved in a solvent having limited solubility in said gasoline and selected from the group consisting of amines and amino alcohols.

ROBERT H. ROSENWALD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,488,000 Bernard Nov. 15, 1949 2,494,687 Bond Jan. 17, 1950 2,508,817 Devol et al May 23, 1950 2,543,953 Backensto Mar. 6, 1951 2,552,399 Browder May 8, 1951 2,556,837 Browder et a1 June 12, 1951 2,560,374 Shmidl July 10, 1951 2,562,767 Browder et a1 July 31, 1951 2,565,349

Browder et a] Aug. 21, 1951 

1. THE PROCESS OF SWEETENING A SOUR HYDROCARBON DISTILLATE WHICH COMPRISES CONTACTING SAID DISTILLATE IN THE PRESENCE OF AIR WITH A PHENYLENE DIAMINE, AN INORGANIC ALKALINE MATERIAL AND A SOLVENT FOR SAID ALKALIE MATERIAL, SAID SOLVENT HAVING LIMITED SOLUBILITY IN SAID DISTILLATE AND SELECTED FROM THE GROUP CONSISTING OF AMINES AND AMINO ALCOHOLS. 